Optical Stimulation of the Facial Nerve: A New Monitoring Technique?

Authors

  • Ingo Ulrik Teudt MD,

    1. Department of Otolaryngology–Head and Neck Surgery, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, U.S.A.
    2. Department of Otolaryngology–Head and Neck Surgery, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
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  • Adam E. Nevel BS,

    1. Department of Otolaryngology–Head and Neck Surgery, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, U.S.A.
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  • Agnella D. Izzo PhD,

    1. Department of Otolaryngology–Head and Neck Surgery, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, U.S.A.
    2. Department of Biomedical Engineering, Northwestern University, Evanston, Illinois, U.S.A.
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  • Joseph T. Walsh Jr PhD,

    1. Department of Biomedical Engineering, Northwestern University, Evanston, Illinois, U.S.A.
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  • Claus-Peter Richter MD, PhD

    Corresponding author
    1. Department of Otolaryngology–Head and Neck Surgery, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, U.S.A.
    2. Department of Biomedical Engineering, Northwestern University, Evanston, Illinois, U.S.A.
    3. Hugh Knowles Center, Northwestern University, Evanston, Illinois, U.S.A.
    4. Department of Communication Sciences and Disorders, Northwestern University, Evanston, Illinois, U.S.A.
    • Dr. Claus-Peter Richter, Department of Otolaryngology–Head and Neck Surgery, Northwestern University, Feinberg School of Medicine, Searle Building 12-561, 303 East Chicago Avenue, Chicago, IL 60611-3008
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  • This project has been funded in part with Federal funds from the National Institute of Deafness and Other Communication Disorders, National Institutes of Health, Department of Health and Human Services, under Contract No. HHSN260 to 2006 to 00006-C/NIH No. N01-DC-6 to 0006 and by the E.R. Capita Foundation.

Abstract

Objectives/ Hypothesis: One sequela of skull base surgery is iatrogenic damage to cranial nerves, which can be prevented if the nerve is identified. Devices that stimulate nerves with electric current assist in nerve identification. Contemporary devices have two main limitations: 1) the physical contact of the stimulating electrode and (2) the spread of the current through the tissue. In contrast to electrical stimulation, pulsed infrared optical radiation can be used to safely and selectively stimulate neural tissue and might be valuable for screening.

Methods: The gerbil facial nerve was exposed to 250 microsecond pulses of 2.12 μm radiation delivered via a 600-μm-diameter optical fiber at a repetition rate of 2 Hz. With use of 27 GA, 12-mm intradermal electrodes, muscle action potentials were recorded. Nerve samples were examined for possible tissue damage.

Results: Eight facial nerves were stimulated with radiant exposures between 0.71 and 1.77 J/cm2, resulting in compound muscle action potentials (CmAPs) that were simultaneously measured at the m. orbicularis oculi, m. levator nasolabialis, and m. orbicularis oris. Resulting CmAP amplitudes were 0.3 to 0.4 mV, 0.15 to 1.4 mV, and 0.3 to 2.3 mV, respectively, depending on the radial location of the optical fiber and the radiant exposure. Individual nerve branches were also stimulated, resulting in CmAP amplitudes between 0.2 and 1.6 mV. Histology revealed tissue damage at radiant exposures of 2.2 J/cm2 but no apparent damage at radiant exposures of 2.0 J/cm2.

Conclusions: The experiments showed that selective muscle action potentials can be evoked optically in the gerbil facial nerve without direct physical contact.

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